SmartSound analyzes your sound environment and automatically applies your personalized audio, Smart Active Noise Cancellation (ANC) and HearThrough settings, to give you the sound you need, when you need it. Smart Active Noise Cancellation (ANC) responds to your environment, switching itself on if it detects unwanted background noise, according to the preferences you set within the Jabra Sound+ app. The headphones contain 8 microphones, 4 of which are used by the powerful digital ANC to filter out the noise around you.